Hotels, motels and other transient residential establishments are constantly confronted with the problem of assuring that their guests are secure in their rooms and that no unauthorized persons will be able to gain access to such rooms when the guests are away. When guests are in their rooms, they are able to use the dead bolt locks or chains usually provided to prevent entry. It would be unduly burdensome for all concerned, however, to require guests to use double keys or submit to tedious identification procedures as an expedient for thwarting would-be thieves or intruders when the guests are not in their rooms. Therefore, continuing efforts have been made to find ways and means of preventing guest room doors from being opened, other than with keys intended for that purpose.
Almost invariably, doors to guest rooms open inwardly. Such doors are provided with spring-loaded latches which engage in suitably aligned apertures in cooperating striker plates on the door jambs. The spring-loaded latch or bolt is provided on the side which first contacts the striker plate with an oblique or slanted face so that as the door is closed, the bolt is caused to retract by reason of the striker plate pressure on the slanted face until the bolt is in position opposite the cooperating aperture in the striker plate, when spring pressure causes the bolt to be thrust into the aperture. The opposite face of the bolt is not slanted, so that in order to operate the retraction mechanism, it is necessary to turn the doorknob engaged therewith to disengage the bolt from the aperture. Normally, the retraction mechanism can be operated only from inside the room without a key. From the outside, it is necessary to use a key to cause the bolt to retract from the striker plate.
The big problem with such locks has been the fact that there is usually enough space between the door and the striker plate, and the trim on the door jamb against which the door is engaged when it is closed, to enable a dextrous person to insert jimmying tools, shims or even flexible plastic credit cards in that space in such a manner as to exert pressure on the slanted face of the bolt and it to retract, thus becoming disengaged from the aperture in the striker plate and allowing the door to be opened.
Locksmiths and others have worked for many years on the problem of finding ways to prevent insertion of jimmying tools or shim-like objects into the space between the door and the striker plate. Some of the means thus devised have employed auxiliary metal strips, of varying cross-sectional shapes, for installation on the door jamb, adjacent the striker plate-sometimes with cooperating or interlocking strips on the door. Examples of such metal strips are found in patents issued to A. Barone, U.S. Pat. No. 3,279,840 granted Oct. 18, 1966, and to E. L. Thompson, U.S. Pat. No. 3,392,999, granted July 16, 1968. Examples of those in which cooperating door strips are used are patents issued to F. M. Sushan, U.S. Pat. No. 3,405,962, granted Oct. 15, 1968, and to Grinbaum, et al., U.S. Pat. No. 3,895,834, granted July 22, 1975.
Previous devices for making doors jimmy-proof have had varying degrees of effectiveness, which was often inversely proportional to their complexity. Therefore, a need has continued to exist for a device to safeguard guest room doors against jimmying and which could combine maximum simplicity with maximum effectiveness.